Improved SOIFO-based rotor flux observer for PMSM sensorless control

A second-order integral flux observer (SOIFO-FLL) with dc component and harmonics attenuation capability is proposed for PMSM sensorless control in this paper. Due to the nonzero integral initial value, parameter mismatch, converter nonlinearities and detection errors, the estimated rotor flux by the conventional methods, pure integrator and low-pass filter (LPF) suffer the dc component and harmonics. And a novel rotor flux estimation method, SOIFO-FLL is proposed on basis of the second-order generalized integrator (SOGI) structure. Combined with the frequency-locked loop (FLL), the dc and high-order harmonics of the estimated rotor flux can be removed by the SOIFO. Lastly, the rotor position are exacted accurately by a quadrature normalized phase locked loop (Q-PLL). Simulations and experimental results verify the excellent performance of the proposed SOIFO-FLL based rotor flux observation and sensorless control strategy.